Flow Deflector

ABSTRACT

The present invention is a flow deflector suitable for a heat exchanger of the type consisting of at least one core made up of tubes forming a bundle arranged inside a shell and at least one baffle. The deflector according to the invention is an easily manufactured part independent from the construction of the bundle of tubes and of the baffle which allows modifying the coolant fluid or liquid flow path with greater freedom than that achieved by combining internal openings in the baffle or baffles. Another object of this invention is the heat exchanger obtained using the deflector for optimising coolant liquid flow path. The application of the invention in heat exchangers for EGR (Exhaust Gas Recirculation) systems is of special interest.

OBJECT OF THE INVENTION

The present invention is a flow deflector suitable for a heat exchangerof the type consisting of at least one core made up of tubes forming abundle arranged inside a shell and at least one baffle. The deflectoraccording to the invention is an easily manufactured part independentfrom the construction of the bundle of tubes and of the baffle whichallows modifying the coolant fluid or liquid flow path with greaterfreedom than that achieved by combining internal openings in the baffleor baffles.

Another object of this invention is the heat exchanger obtained usingthe deflector for optimising coolant liquid flow path.

The application of the invention in heat exchangers for EGR (Exhaust GasRecirculation) systems is of special interest.

BACKGROUND OF THE INVENTION

The configuration of heat exchangers for EGR systems usually consists ofa bundle of tubes through which the recirculated gas passes and of ashell housing said bundle of tubes. A coolant fluid circulates betweenthe bundle of tubes and the shell such that the gas circulating throughthe tubes transfers heat to the coolant liquid.

In most cases the entry of the coolant liquid occurs at one point of theshell corresponding to an end of the bundle; and the exit at anotherpoint of the shell located at the opposite end of the bundle. The entrythrough a point establishes regions of the volume occupied by thecoolant liquid which are stagnation regions. Since the speed is zero orvery small in stagnation regions, convection is very low and thereforeheat dissipation to other areas does not occur. As a result, thetemperature is higher in these areas and worse still the materials whichare in contact with these stagnation regions suffer greater thermalstresses. As a result of these high stresses in localised sites of thedevice, the service life of the materials is unfailingly reduced sincethey withstand a lower number of thermal fatigue cycles.

A decrease in thermal stress level implies an increase in the number ofthermal fatigue cycles withstood by the device without itmalfunctioning. This increase in thermal fatigue cycles withstood by thedevice follows the behaviour similar to that of an exponential function.The decrease in thermal stresses and therefore in thermal fatigue, andthe subsequent increase in the exchanger durability is achieved by meansof a homogenous temperature distribution especially in the hotter areas.

To prevent the existence of stagnation regions, flow deflection meansare incorporated, for example, for moving the coolant liquid in a zigzagmanner and increasing its speed and thus improving heat convection.

This flow deflection is achieved by means of the shape of the inneropenings of the baffles responsible for securing the tubes of the bundleof tubes assuring a specific separation between said tubes. The morecommon configuration of these baffles is that of a perimetricring-shaped die-cut plate according to the configuration of theperimeter of the bundle of tubes; and, having elongations towards theinside of the comb-shaped perimetric ring. These comb-shaped elongationsare intended for being housed between the tubes of the bundle andprevent the passage of the coolant liquid through them.

If the elongations are short the opening left by these elongationsinside the bundle are larger. The flow passing through these baffles isforced to follow the path imposed by the position and size of theopenings by combining several baffles with different internal openings,the openings defining the ends of these elongations. For example,placement on alternate sides of the internal openings will give rise toa zigzag path.

Even though it reduces the existence of stagnation regions this solutionhas significant limitations as detailed below.

Incorporating the baffles to the bundle of tubes allows assuring thedistances between tubes. Manufacturing is carried out by die-cuttingsheet metal which is welded to this bundle. If the comb-shapedelongations of the baffles are excessively styled the manufacturingcomplexity increases given that dimensional stability and the tolerancesdemanded by mass production are more difficult to achieve.

Increasing the internal distance between tubes allowing wider andtherefore stiffer and more stable elongations is a possible option whenfaced with this problem. This solution has the drawback of reducing theamount of tubes which can be bundled into one and the same volume andtherefore the efficiency is severely reduced.

Reducing the length of the comb-shaped elongations is also possible. Thedrawback of this alternative is that the distribution of coolants isworse since the flow deflection and interaction are lower.

Other additional limitations of the baffles is the need of beingarranged essentially perpendicular to the tubes of the bundle of tubestherefore the deflection is not always optimum and the pressure lossesare higher than if oblique flow deflections could occur.

In order to solve these problems the present invention uses a partintended for being secured, preferably by clipping, in an alreadyexisting baffle the configuration of which is not limited bymanufacturing demands, by geometry limitations of a part obtained bydie-cutting sheet metal, and by limitations of baffle welding.

DESCRIPTION OF THE INVENTION

The present invention solves the problems identified above by using apart which can be manufactured in plastic, resin or other materials,intended for being installed, preferably by clipping, on a baffle. Inthis case the baffle can be of very simple design since it is no longerrequired to be responsible for coolant fluid or liquid flow deflection.The part according to the invention is a flow deflector suitable for aheat exchanger of the type consisting of at least one core made up oftubes forming a bundle arranged inside a shell and at least one baffle,such that said deflector comprises:

-   -   a main body extending along an X-X direction,    -   This main body extends on the edge of said baffle when the        deflector is operatively installed on the baffle. Given that the        baffle is arranged perpendicular to the tubes of the bundle, the        direction identified as X-X will correspond both to the        transverse direction and to the direction in which the mentioned        main body extends.

The X-X direction is a geometric reference for the remaining componentsof the deflector of the invention.

-   -   a plurality of at least three fixing elongations protruding        transversely with respect to the X-X direction of the main body        defining a main plane P containing the X-X direction, wherein        such fixing elongations are such that:        -   they are formed by two groups, a first group of fixing            elongations and a second group of fixing elongations such            that the first group of fixing elongations is distributed            along the X-X direction and located on one side of the main            plane P; and wherein the second group of fixing elongations            is distributed along the X-X direction in positions            different from the positions of the elongations of the first            group of fixing elongations and located on the opposite side            of the main plane P,        -   each of the elongations is arranged at least in a sector            away from the main plane defining a housing such that the            set of housings of the elongations is suitable for housing a            sector of baffle of the heat exchanger for fixing the flow            deflector,

Once the X-X axis has been defined, the position and orientation of theplurality of fixing elongations also defines the main plane P containingthe X-X direction.

When the deflector is placed on the baffle, the fixing elongations areresponsible for attaching the deflector to the bundle of tubes. Theplane P coincides with the main plane of the baffle in this one and thesame operating position of the deflector on the baffle. The condition ofdistributing fixing elongations on both sides of plane P results in theoperating position with a distribution of such elongations on both sidesof the baffle.

The relative movement between the deflector and the bundle of tubes inthe direction perpendicular to the bundle is prevented by resting themain body on the baffle. The exit direction is limited by the existenceof the shell or, as will be seen in the embodiments, by particular waysof making these fixing elongations which incorporate staggerings tosecure the clipping.

The distribution on both sides of the main plane prevents the relativemovement in the direction coinciding with the direction of the tubes ofthe bundle.

Lastly, movement parallel to the X-X direction is prevented because thefixing elongations are inserted between the tubes of the bundle inoperating mode. Nevertheless, according to the embodiments which will bedescribed below, some of these fixing elongations, preferably the endfixing elongations can have reinforcements limiting movements in thisdirection to the greatest extent possible.

The way in which the elongations are distributed on both sides of theplane is such that they leave a spacing to allow housing the baffle. Ina view of the part according to the X-X direction, this spacing is shownin projection in an area which allows accommodating the section of thebaffle on which the deflector is fixed by means of the fixingelongations.

-   -   deflecting extensions suitable for being located in the spaces        located between the tubes of the core made up of tubes of the        heat exchanger suitable for modifying the coolant flow path.

Once the deflector is fixed on the baffle, the part of the deflectorwhich intervenes by modifying the coolant fluid flow path is thedeflecting extensions. The position thereof depends on the particularembodiment. Two particular examples will be shown below, although therecan be more; a first example in which the deflecting extensions arelocated at the end of the fixing elongations giving continuity to suchelongations; and a second example in which these deflecting extensionsare located on one side of the main plane P linked to the main body bymeans of a resistant bridge. This second embodiment gives no reason forflow deflection to occur in the position of the baffle. Likewise, thesedeflecting extensions can adopt degrees of inclination or curvaturewhich would not be possible, or would be very complicated, to impose onone part of the baffle. These extensions, given that they do not have tobe attached to the tubes of the bundle, can cover the entire widthdefined by the gap between the tubes producing total flow deflection; orthey can partially cover the width for example for allowing the passageof coolant liquid flow and preventing stagnation regions therebehind.

DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will be seenmore clearly from the following detailed description of a preferredembodiment provided only by way of illustrative and non-limiting examplein reference to the attached drawings.

FIG. 1 shows an embodiment according to the state of the art of a heatexchanger for cooling EGR gases by means of a coolant liquid. A zigzagcoolant liquid flow is imposed by means of baffles as shown by the linewith arrows.

FIG. 2 shows a baffle according to an example of the state of the artwith comb-shaped elongations which do not need to have the same length.The length of the ends of these elongations defines the size of theopening for coolant liquid passage.

FIGS. 3 a and 3 b show a bundle of tubes of a heat exchanger from whichthe outer shell has been removed. FIG. 3 a shows a deflector accordingto a first embodiment before being fixed to a baffle of the bundle oftubes. FIG. 3 b shows the same part once inserted and in an operatingposition.

FIGS. 4 a, 4 b, 4 c and 4 d show an elevational view, profile view andtwo different perspective views of the same deflecting part according tothe first embodiment.

FIG. 5 shows a side perspective view of the deflector according to asecond embodiment orientated towards the bundle of tubes and the baffleto allow observing the most relevant attachment means and elements ofits structure.

FIG. 6 shows the same embodiment as in the preceding figure only thatthe angle of the perspective is slightly rotated to allow observingdetails which cannot be observed in the preceding perspective.

FIG. 7 shows a sector of the bundle of tubes of a heat exchanger withthe baffle and the deflecting part according to the second embodimentbefore being inserted.

FIG. 8 essentially shows the same as in the preceding figure only thatthe deflecting part is shown already fixed on the baffle.

FIG. 9 shows a cross-section with respect to the X-X direction accordingto a plane passing between two tubes of the bundle of tubes of theexchanger to allow observing the position of the fixing elements and ofthe deflecting extensions in their operating position.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a heat exchanger according to the state of the art formedby a core (2) and a shell (3) where coolant liquid flow is directed bymeans of baffles (2.2) for the purpose of increasing heat convection andtherefore exchanger efficiency. The existence of stagnation regions inthe coolant liquid flow means that the liquid which is in saidstagnation region raises its temperature reaching boiling temperature.

Such effects cause material fatigue and breakage drastically reducingthe service life of the device.

The baffles (2.2) are resistant elements which must be welded to thebundle (2) of tubes (2.1). The manufacturing and welding requirements donot have to be compatible with the deflection surface requirements andtherefore do not allow defining an optimum flow configuration.

FIG. 2 shows a baffle (2.2) incorporating comb-shaped elongationsintended for being housed between the tubes (2.1) of the bundle (2)covering the space defining the separation between the tubes. The endsof the comb-shaped elongations are the edges of the internal windowthrough which the passage of the coolant liquid is allowed. The passageand path of the coolant liquid can be modified by alternating the areasand positions of these windows but it has the drawbacks alreadymentioned in the state of the art.

The present invention uses a part, the deflector (1), intended for beingincorporated in a baffle (2.2) where this baffle (2.2) is very simple tomanufacture since it does not require thin and long elongations formodifying inner coolant liquid flow.

A first embodiment of the invention is shown in detail in FIGS. 4 a, 4b, 4 c and 4 d. FIGS. 4 a and 4 b are the elevational, profile view ofthis first example whereas FIGS. 4 c and 4 d are two perspective viewswhich allow observing the same part (1) from almost opposite positionsfor offering visual access to all the details.

Before describing this embodiment in detail, the deflector (1) accordingto this first embodiment is seen before and after being inserted in itsoperating position by means of FIGS. 3 a and 3 b. In FIG. 3 a thedeflector (1) is located on the baffle (2.2) such that in this view itis possible to see the protruding edge of the baffle (2.2) on which thedeflector (1) will be located. In this embodiment, the baffle (2.2) hasa configuration with short internal elongations such that it does notlimit the flow of coolant liquid through it.

Using FIGS. 4 a-4 d it is seen that the deflector (1) comprises a mainbody (1.1) extending along the X-X direction. The main body (1.1) isintended to rest on the baffle (2.2) and the elongations (1.2, 1.3)which allow fixing on the baffle (2.2) protrude from the main body. FIG.4 b shows the main plane P, which in this embodiment coincides with theplane of symmetry, leaving a group of fixing elongations (1.2) on oneside and the remaining fixing elongations (1.3) on the other side. Thissame view 4 b as well as the perspective view 4 d allow observing thespacing of the fixing elongations (1.2, 1.3) with respect to plane P andtherefore the separation between both groups of elongations. Saidseparation gives rise to a housing (H) for the sector of baffle (2.2)resulting in a fixing mode between both elements (1, 2.2).

In the particular case of this embodiment, each of the fixingelongations (1.2, 1.3) has a deflecting extension (1.2.2, 1.3.2)configured as a continuation of the fixing elongation (1.2, 1.3). In theattachment between the fixing elongation (1.2, 1.3) and the deflectingextension (1.2.2, 1.3.2) there is a staggering arranged on the innerside orientated towards the main plane P. This staggering is intendedfor resting on the end of the elongations of the baffle (2.2) assuringtheir retention and preventing them from coming out.

In other cases, instead of using this staggering it is possible for themain body (1.1) to rest on the internal face of the shell (3) of theheat exchanger.

The ends of the deflecting extensions (1.2.2, 1.3.2) of this embodimentare bevelled on the inner side orientated towards the main plane P. Thisbeveling allows the insertion on the baffle (2.2) during assemblyfacilitating the opening by means of bending the set formed by thedeflecting extension (1.2.2, 1.3.2) and the fixing elongation (1.2,1.3). The insertion is completed when the sector of baffle (2.2) whichis housed in the housing (H) overcomes the staggerings (1.2.1, 1.3.1)allowing the shape recovery of the set of fixing elongations (1.2, 1.3)together with the deflecting extensions (1.2.2, 1.3.2). In thisembodiment, a material with elastic behaviour in the range ofdeformations imposed by the thickness of the baffle (2.2) and thedifferent dimensions of the deflector (1) intervening in the insertionhas been selected for allowing an easy shape recovery.

A second embodiment is shown in detail in FIGS. 5 and 6. According tothis embodiment the main body (1) extends according to the X-X directionand comprises a channel (1.6) which also extends in the X-X directionintended for housing the outer edge of the baffle (2.2) when thedeflector (1) is installed on the baffle (2.2).

FIG. 5 shows a perspective view of the main plane P passing in the X-Xdirection and leaving the fixing elongations (1.2, 1.3) on both sides.In this particular case the fixing elongations (1.2, 1.3) are shown ingroups of three, and in each group of three, two fixing elongations(1.3) are on one side and the third fixing elongation (1.2) is on theopposite side of the main plane P. This third fixing elongation (1.2) isarranged between the other two fixing elongations (1.3) following theX-X direction. Only three fixing elongations (1.2, 1.3) would thus besufficient for assuring a fixing preventing movements in directionsperpendicular to the X-X direction and even rotational movements.

In this embodiment the beveling which facilitates the insertion of thedeflector (1) in the baffle (2.2) is in the fixing elongations (1.2,1.3).

A resistant bridge (1.4) at the end of which a plurality of deflectingextensions (1.5) starts extends from the main body (1.1). In thisembodiment there are as many deflecting extensions (1.5) as there arecavities between tubes (2.1) such that each deflecting extension (1.5)is intended for entering a space between tubes (2.1). Additionally,there are two end side extensions with reinforcement (1.5.1) suitablefor externally supporting the bundle (2) of tubes (2.1) and alsocovering the space between the bundle (2) of tubes (2.1) and the shell(3). The space between tubes (2.1) is narrower than the space betweenthe bundle (2) of tubes (2.1) and the shell (3). The lower flowresistance in this second space means that the entire flow tends tocirculate outside the bundle of tubes (2.1). The presence ofreinforcement (1.5.1) covering the space between the bundle (2) of tubes(2.1) and the shell (3) has the effect of forcing the flow to circulatebetween the tubes (2.1) increasing the cooling efficiency.

With respect to the deflecting extensions (1.5), in this embodiment,they have a width slightly less than the space between tubes (2.1)giving rise to a clearance. Although the deflecting extensions (1.5)divert the flow reaching them, the existence of a clearance allows asmall part of the flow to pass between the deflecting extension (1.5)and the tube (2.1) preventing stagnation regions which would give riseto points which could easily reach boiling temperature behind thedeflecting extension (1.5).

In this embodiment, the deflecting extensions (1.5) elongate by way ofribs until reaching the main body (1.1).

FIG. 8 shows the bundle (2) of tubes (2.1) after having removed theshell (3) with the flow deflector (1) before being inserted on thebaffle (2.2). The fixing elongations (1.2, 1.3) enter the spaces betweentubes (2.1) being located on both sides of the baffle (2.2) by means ofthe downwards movement thereof (moving downward according to theorientation shown in the figure). In turn, the deflecting extensionsalso enter the spaces between the tubes (2.1) reaching the finalposition which is shown in FIG. 8. This figure shows two baffles (2.2);nevertheless, flow deflection does not occur in the position of thebaffles (2.2) but in the position where the deflecting extensions (1.5)are located which, as a result of the resistant bridge (1.4), are awayfrom the baffle (2.2). The design requirements for positioning thebaffles (2.2) based on resistant criteria thus do not impose theposition of the deflecting extensions (1.5) this second positiondepending on flow criteria to be imposed on the coolant liquid so thatthe heat exchange is carried out efficiently and without stagnationregions.

FIG. 9 shows a section of the heat exchanger according to a plane whichis orientated in the direction of the tubes (2.1) of the bundle (2). Thetubes (2.1) are essentially planar. This section allows observing howthe deflecting extensions (1.5) reach approximately the width of one ofthe two tubes (2.1) giving rise to the total height of the bundle (2) oftubes (2.1). The flow will be diverted so that it will be redirected tothe lower tubes (2.1) (also following the orientation shown in thedrawing). In this embodiment, the deflecting surfaces are inclined sothat the diverted flow has an axial component according to the main axisof the bundle (2) of tubes (2.1). Nevertheless, these extensions canadopt other more complex configurations such as curves imposing aspecific configuration to the stream lines.

1. A flow deflector suitable for a heat exchanger comprising at leastone core made up of tubes forming a bundle (2) arranged inside a shelland at least one baffle, such that said deflector comprises: a main body(1) extending along an X-X direction, a plurality of at least threefixing elongations (1.2, 1.3) protruding transversely with respect tothe X-X direction of the main body (1) defining a main plane (P)containing the X-X direction, wherein such fixing elongations (1.2, 1.3)define two groups, a first group of fixing elongations (1.2) and asecond group of fixing elongations (1.3) such that the first group offixing elongations (1.2) is distributed along the X-X direction andlocated on one side of the main plane (P); and wherein the second groupof fixing elongations (1.3) is distributed along the X-X direction inpositions different from the positions of the elongations of the firstgroup of fixing elongations (1.2) and located on the opposite side ofthe main plane (P), wherein each of the elongations (1.2, 1.3) isarranged at least in a sector away from the main plane (P) defining ahousing (H) such that the set of housings (H) of the elongations (1.2,1.3) is suitable for housing a sector of baffle (2.2) of the heatexchanger (2) for fixing the flow deflector (1), and deflectingextensions (1.2.2, 1.3.2, 1.5) suitable for being located in the spaceslocated between the tubes (2.1) of the core made up of tubes of the heatexchanger (2) and suitable for modifying the coolant flow path.
 2. Thedeflector according to claim 1, characterised in that the fixingelongations (1.2, 1.3) are distributed in groups of 3 elongations, twoelongations belonging to one of the first or second group of fixingelongations (1.2) and one belonging to the other of the first or secondgroup of fixing elongations (1.3).
 3. The deflector according to claim 1or 2, characterised in that the deflecting extensions (1.2.2, 1.3.2) areextensions of the fixing elongations (1.2, 1.3).
 4. The deflectoraccording to claim 3, characterised in that the transition between atleast one fixing elongation (1.2, 1.3) and the deflecting extension(1.2.2, 1.3.2) is by means of a step (1.2.1, 1.3.1) suitable to allowresting on the edge of the baffle (2.2) arranged inside the bundle (2)of tubes (2.1) of the heat exchanger (1).
 5. The deflector according toclaim 1, characterised in that the main body (1) extends by means of aresistant bridge (1.4) to one side of the plane (P) and in a directiontransverse to the X-X direction such that at the end of said resistantbridge (1.4) there are located deflecting extensions (1.5) beingorientated such that in the operating position they are located in thespaces between the tubes of the bundle (2) of tubes (2.1) of the heatexchanger (2).
 6. The deflector according to claim 5, characterised inthat the deflecting extensions (1.5) are inclined with respect to thedirection perpendicular to the direction in which the resistant bridge(1.4) extends.
 7. The deflector according to claim 5, characterised inthat the deflecting extensions (1.5) are elongated by means ofreinforcement ribs to the group of fixing elongations (1.2, 1.3)arranged on the side of the plane (P) coinciding with the side to wherethe resistant bridge (1.4) extends.
 8. The deflector according to claim5, characterised in that the main body (1) comprises a channel (1.6)arranged in the X-X direction suitable for housing the edge of thebaffle (2.2).
 9. The deflector according to claim 1, characterised inthat one or more deflecting extensions (1.2.2, 1.3.2, 1.5) has areinforced sector for fitting in the space between the tubes.
 10. Thedeflector according to claim 5, characterised in that the end arrangeddeflecting extensions (1.2.2, 1.3.2, 1.5) have a reinforced sector(1.5.1) for resting on the outer surface of the bundle (2) of tubes(2.1).
 11. A heat exchanger comprising at least one core made up oftubes (2.1) forming a bundle (2) arranged inside a shell for thecirculation of a coolant fluid between the bundle (2) of tubes (2.1) andthe shell such that the bundle (2) comprises at least one baffle (2.2)for maintaining the separation between the tubes of the bundle (2) oftubes (2.1) this baffle (2.2) being formed, at least on one of itssides, by a plate sector with an edge protruding from the bundle (2)being extended according to a direction (X-X) transverse to thedirection of the tubes of said bundle (2) and wherein the plate has anopening arranged inside the bundle (2) for the coolant fluid to passthrough it and comprising at least one flow deflector according to claim1.